Constraints on the Stellar/Substellar Mass Function in the Inner Orion Nebula Cluster

Abstract

We present the results of a FWHM imaging survey at K (2.2 km) and H (1.6 km) covering 0A .5È0A .9 centered on h1C Ori, the most massive star in the Orion Nebula Cluster (ONC). At the age D5@ .1 ] 5@ .1 and distance of this cluster, and in the absence of extinction, the hydrogen-burning limit (0.08 M _ ) occurs at K B 13.5 mag, while an object of mass 0.02 has K B 16.2 mag. Our photometry is com-M _ plete for source detection at the 7 p level to K B 17.5 mag and thus is sensitive to objects as low-mass as 0.02 seen through visual extinction values as high as 10 mag. We use the observed magnitudes, M _ colors, and star counts to constrain the shape of the inner ONC stellar mass function across the hydrogen-burning limit. After determining the stellar age and near-infrared excess properties of the optically visible stars in this same inner ONC region, we present a new technique that incorporates these distributions when extracting the mass function from the observed density of stars in the K[(H[K) diagram. We Ðnd that our data are inconsistent with a mass function that rises across the stellar/ substellar boundary. Instead, we Ðnd that the most likely form of the inner ONC mass function is one that rises to a peak around 0.15 and then declines across the hydrogen-burning limit with slope M _ , N(log M) P M0.57. We emphasize that our conclusions apply to the inner 0.71 pc ] 0.71 pc of the ONC only ; they may not apply to the ONC as a whole where some evidence for general mass segregation has been found.

A Vla Survey for Faint Compact Radio Sources in the Orion Nebula Cluster

“…The field of view of the JVLA antenna primary beam at 6 cm, FWHM of 9′, encompasses all 778 YSOs from Hillenbrand & Carpenter (2000), and all of the 196 HSTdetected proplyds (Ricci et al 2008). 141 of the 196 HSTdetected proplyds are also detected as sources in Hillenbrand & Carpenter (2000).…”

“…141 of the 196 HSTdetected proplyds are also detected as sources in Hillenbrand & Carpenter (2000). We, therefore, use a single pointing to image the field at 6 cm.…”

“…We can also use catalogs of previously known source positions to target our search. We search our maps at the positions of >700 near-infrared-detected sources (Hillenbrand & Carpenter 2000) and ∼200 HST-detected proplyds (Ricci et al 2008, with an overlap of about ∼150 of the near-infrared detected sources). We also search the coordinates of known submillimeter sources detected with the SMA, CARMA, and ALMA that lack counterparts at infrared wavelengths (Eisner et al 2008;Mann & Williams 2010;Mann et al 2014).…”

“…Near-infrared surveys of the ONC find >700 young stellar objects (YSOs), most of which are likely to harbor protoplanetary disks (Hillenbrand & Carpenter 2000). Hubble Space Telescope (HST) images of the ONC also reveal ionized disks and dusty disks silhouetted against the backdrop of nebular emission (e.g., O'Dell & Wen 1994;Bally et al 1998a;Smith et al 2005;Ricci et al 2008).…”

Commission 37: Star Clusters and Associations: (Amas Stellaires Et Associations)

“…One of the best targets is the Inner Orion Nebula Cluster. From H,K observations, Hillenbrand & Carpenter (2000) find that their data are inconsistent with a mass function that rises across the stellar/substellar boundary. Instead, they find that the most likely form of the mass function is one that rises to a peak around 0.15 MQ, and then declines across the hydrogen-burning limit.…”